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The diving suit created in 1715 by the knight Pierre Rémy de Beauve.
Photo Alain Weill © Collections Musée Frédéric Dumas – Ville de Sanary-sur-Mer.

A riddle at the bottom of the Mediterranean Sea found during underwater exploration of the Lighthouse of Alexandria. © Stéphane Compoint.

Christian RÉGNIER, MD
Practicien Attaché des
Hôpitaux de Paris, Société
Internationale d’Histoire de la
Médecine, 9 rue Bachaumont
75002 Paris, FRANCE
(e-mail:
dr.christian.regnier@wanadoo.fr)

“No conditions exist in nature where man and air-breathing creatures are subjected to the influence of a stronger pressure than that exerted by the atmosphere on the seas,” wrote Paul Bert, the French physiologist and expert in nitrogen narcosis, in 1878. This observation marked the beginning of underwater medicine and the complex study of the physiological phenomena linked to decompression. Other than pearl fishermen and breath-hold divers (apnea divers) hunting fish in Asia or Polynesia, extended underwater diving using a system of artificial breathing dates back to the first industrial revolution in the middle of the 19th century. In the 18th century, the first diving suits were connected to the surface by a hose through which air was transported via the use of a bellows or a manual pump located at the surface. In 1865, the first autonomous diving suit, designed by three French engineers (Benoît Rouquayrol and Augustus and Louis Denayrouze), appeared; it was fitted with a regulator and reserve of air. It was then that the era of underwater diving truly began, but both this and increasingly ambitious civil engineering projects requiring the use of pressurized caissons were taking their toll of decompression accidents. It was therefore essential to improve the equipment, but above all to gain an understanding of the biophysics of blood gas dissolution and depressurization. Several European and American contributions helped further the quest by establishing diving tables outlining the stages of decompression, by carrying out studies on the composition of diving gases, and by designating rules to follow while descending into the depths and returning to the surface. With the partial resolution of diving equipment and safety questions by the middle of the 20th century, the exploration of the sea and river depths commenced. Several French pioneers, namely Philippe Tailliez, Jacques-Yves Cousteau, and Frédéric Dumas, were instrumental in the forging of this new path of scientific adventure and also in raising awareness in our collective consciousness about the protection of marine ecosystems.

Nowadays underwater diving, which boasts 15 million divers worldwide, makes use of techniques and equipment that are a result of technology that has been under continuous development since the middle of the 19th century. The diving suit used most often today is the independent, flexible, self-contained model, while rigid suits and helmets are also occasionally used. A breathable circuit can be one of two types; an open circuit is one where a diver produces bubbles each time an exhalation is ejected into the sea, while a closed circuit is one where each exhalation is recycled to produce more oxygen, which then reenters the same supply circuit of breathable gas as before.^1,2

On the medical front, doctors were confronted early on with diving accidents that were the result of large variations in pressure that had affected the hollow cavities of the body. Themain factor affecting a diver’s body in these cases is the pressure exerted by seawater. Pressure increases by one bar for every ten meters’ depth. Because most of the components of the human body are incompressible, the body’s cavities that come in contact with inhaled air, such as the ears, sinuses, teeth, and intestines, are particularly vulnerable.^2-4

This can have several serious implications. For example, a difference in pressure or unequal pressure in the middle ear is likely to cause alternobaric vertigo, which can be fatal if it causes a diver to panic. In order to compensate for barometric pressure variations in the internal ear during descent, the diver must perform the maneuver described by the Italian surgeon Antonio Maria Valsalva (1666-1723), which now carries his name, the Valsalva Maneuver. Additionally, the air contained in the lungs expands as the diver ascends, which can cause serious tissue lesions. Secondly, the narcotic properties of some gases (argon, nitrogen), which are responsible for “drunkenness of the deep,” are counteracted by the use of a gaseous mixture rich in oxygen, such as Nitrox, the composition of which is adjusted according to the depth of the dive.^1,4,5

Finally, the main problem that doctors faced in the 19th century was decompression. An inert gas (eg, nitrogen, helium, or hydrogen) dissolves in a liquid—in this case, the blood of the diver—according to its partial pressure (Henry’s Law), which increases with the depth of the dive. Inversely, during ascent, gas escapes into the liquid causing bubbles to form, which can bring on circulatory accidents, paralysis, and articular or joint pain, which are typical types of decompression disturbance. The diver must therefore ascend carefully in defined stages to avoid the onset of such effects.^4,6

Divers avoid decompression sickness or caisson disease or “the bends,” caused by the formation of gas bubbles in the body, by decreasing water pressure on the body slowly at the end of the dive and allowing gases trapped in the bloodstream to gradually break solution and leave the body, a process called “offgassing.”

A history of pressure and decompression

For centuries, the pearl fishermen of Polynesia have been familiar with the risks involved in ascending too quickly after immersion at 40 meters. The knowledge and stories passed on by the elders and ancestors of the fishermen comprised one crucial rule, the establishment of decompression stages. This was done in order to appease the Ocean God, who was held responsible for such diving mishaps. The same instinctive mastery of decompression rules is attributed to the Ama apnea divers in Japan and the Haenyo from the province of Jejudo in Korea.^3,7

The first recorded observation of the physiological consequences of decompression, now known as decompression illness (DCI), was made in 1667 by the Irish physicist and chemist Robert Boyle (1627-1691), when he put a viper in a vacuum under a bell jar. Boyle was one of the pioneers, along with Thomas Hobbes (1588-1679), who carried out experiments in a vacuum. Besides the respiratory distress of the snake, “which struggled furiously,” the scholar noticed that bubbles appeared inside the cornea of the reptile. He attributed this first degassing incident to abrupt decompression. Independently of one another, Robert Boyle and the French physicist abbot Edme Mariotte (1620-1684) both described the law of thermodynamics linking the absolute pressure and volume of a gas to an initial and final state, p1×V1= p2×V2. The Boyle-Mariotte Law only applies to ideal or perfect gases. Following Boyle’s findings, other scientists made related empirical observations:
_ The Englishman Dr Henshaw used a pressurized chamber he invented— the domicilium—to treat pulmonary and intestinal disturbances in 1662;
_ Edmund Halley dived to a depth of 18 meters for 90 minutes in a diving bell experiment in 1689.^1-3,5

In 1803, the physicist and chemist William Henry (1775-1836) made his law public: at a constant temperature and at saturation, the quantity of gas dissolved in a liquid is proportional to the partial pressure the gas exerts on the liquid. In his law, Henry added a specific factor for each gas taking into account its ability to dissolve in a liquid. Henry’s Law found an immediate application in underwater diving and made it possible to understand why decompression accidents occurred when rising to the surface.^1-3

In the middle of the 19th century, England, the United States, and France suffered a large number of fatal accidents with divers, laborers working in caissons in naval shipyards, and coal miners in pressurized atmospheres. In 1847, the notion of decompression was clarified by the French occupational health doctors Pol and Watelle. They observed that being in a high pressure environment immediately following a stay in the deep considerably improved the undesirable symptoms, which opened the way to the perfection of decompression chambers. In 1861, Bucquoy issued the first hypothesis on bubbles in the blood of the divers:

Robert Boyle (1627-1691), regarded as the first modern chemist.

Disturbances linked to stays in the deep are called the bends, an English word meaning “to fold” or “to bend over”. It was used by Triger in 1841 to describe the problems suffered by the tube laborers working on the big American bridges in San Francisco and Mississippi. After a seven-hour stay in tubes with a pressure of three bars, the workers came out bent in two or folded over because of agonizing joint pain. These rheumatological manifestations could also be accompanied by urinary retention, paralysis, palpitations, loss of consciousness, and marrow lesions. The complete clinical chart was drawn up in 1859 by Dr François, who recorded 133 cases of the bends in laborers working on the pile foundations for the bridge from Strasbourg to Kehl.^2,3,8

In 1879, in his monumental 1800-page classic La pression barométrique (Barometric Pressure), Paul Bert (1833- 1886), a French physiologist and politician, explained the role of nitrogen and carbon dioxide gas in decompression accidents. He also described the neurotoxicity of oxygen at high pressure, known as the Paul Bert effect. He was the first to set forth decompression rules for divers:

As for the tube workers, hemade them undergo half to one hour’s worth of decompression, depending on the pressure they had been working at.^5,9,10

Haldane and his tables: debates and controversy

In 1906, with the development of submarines and a corps of military divers, the British Admiralty entrusted the Scottish doctor John Scott Haldane (1860-1936) with the task of studying ways to decrease underwater accidents. He chose to use goats as the experimental model because their lean-fat ratio was relatively similar to that of humans; in addition, goats have a rate of perfusion close to that of man.

Using Henry’s Law (1803), the scholar established a formula to determine the different coefficients of gas absorption in the tissue of an organism. The Scottish scholar continued the work of Paul Bert and confirmed the theory and benefits of a slow ascent by proving that the partial pressure of nitrogen was related to external pressure. To ensure a safe ascent without accidents or adverse effects, he deemed it necessary to respect the following rule: the pressure of nitrogen blood saturation must always be less than or equal to twice the ambi- ent pressure. But in the end, Haldane departed from the hypothesis that the absorption and elimination rate for gases in tissue were identical.^1,2,6

French physician and physiologist Paul Bert (1833-1886), back row, third from left, with mustache, attending an anatomy lesson by Claude Bernard, (back row, fifth from left, with white lab apron).

In 1908, in The Journal of Hygiene, Haldane presented the Royal Navy with his famous diving decompression tables that established stages during ascent to the surface from a depth of up to 62 meters. These tables took into account the age and stoutness of the diver. Haldane’s views contrasted with the theories of Heller, Mager, and von Schrotter, who recommended a slow and uniform ascent of 20 minutes per atmosphere of pressure.

Haldane was the first to provide a mathematical model of decompression and divers adopted his decompression tables rapidly, which resulted in a considerable decrease in diving accidents. “Haldane’s method, thanks to its approximation and the indeterminate nature of its parameters, makes it adaptable to all situations,” wrote Dr Stephane Loiseau in his 2002 memoire of subaquatic and hyperbaric medicine.^6,8,9

Following Haldane,many othermodels were presented. These took into account tissue specificity (Hempelman, Royal Navy, 1952), the variability of thresholds of critical sursaturation in depth (Workman, US Navy, 1965), and the Doppler-detected presence of circulatory venous bubbles (Spencer, US Navy, 1970).^2,8

The Rouquayrol-Denayrouze diving apparatus: a step towards autonomy

In 1865, Benoît Rouquayrol (1826-1875) and Augustus Denayrouze (1837-1883), both natives of the Aveyron area of France (Midi-Pyrénées region), completed construction of the first independent underwater breathing apparatus equipped with an air tank and an air-on-demand regulator. The riveted brass reservoir contained 35 liters at 30 bars of pressure, which allowed a duration of autonomy of 30 minutes at 10 meters.^5,11,12

Scottish physiologist John Scott Haldane (1860-1936) invented the first gas mask used in World War I.

Rouquayrol, a mining engineer for the Company of Coalmines and Foundries of the Aveyron, embarked upon research on ways to help victims of mine disasters, such as firedamp explosions or miners trapped in galleries flooded by gases or water. Between 1860 and 1863, he submitted three patents for a salvaging device to save miners in gaseous environments. These devices were regulators of compressed gas, a mask with nose clip and mouth piece in vulcanized rubber, and a special air pump that compressed air without excessively heating it.^3,11,12

Denayrouze was a Lieutenant in the Navy. Ineligible for active duty after a serious ailment contracted in the region of Cochinchina in southern Vietnam, he spent time recovering in Espalion in southern France, where he met Rouquayrol in 1864. The naval officer immediately grasped that themining engineer’s rescue device could be adapted for underwater diving.^11,12

The two men set to work and came up with the “Rouquayrol- Denayrouze diving apparatus,” for which they registered a patent on June 27, 1864. The regulator was fitted with an antireturn valve for the supply of compressed air. One technical improvement was the addition of a whistle to alert the diver to when the air supply was running low. The first trials were carried out in the Lot area by “cabussairs”, Aveyron poachers who dive into rivers to capture fish trapped in the tall grass. Even though the trials were conclusive, two major technical problems quickly became apparent: the lack of eye protection and the cold temperature of the water, which rapidly paralyzed the divers. Rouquayrol and Denayrouze quickly set about making diving suits using vulcanized rubber from the American Charles Goodyear. To this, they also added goggles based on a design for railway engineer goggles. This diving suit conjured up images of a frogman, but without the flippers. The divers, at this point in time, were still just moving up and down.^11,12

In February 1865, a company was created to sell this innovative equipment to national navies and fishing associations. Two years later, the diving apparatus of the two Aveyronnais inventors was awarded the gold medal at the 1867 Exposition Universelle (World Fair). The renowned French novelist Jules Verne (1828-1905) used this type of equipment to outfit his hero, Captain Nemo, in his novel Twenty Thousand Leagues under the Sea (1869-70). More than 1500 sets of “Rouquayrol- Denayrouze diving apparatus” were sold, and their equipment remained in use for nearly sixty years.5,11,12

In 1864, two Frenchmen, Rouqayrol (a mining engineer) and Denayrouze (a Navy lieutenant) invented the first independent breathing apparatus consisting of a copper (tin inside) diving set with a backpack spherical 8-liter air tank that supplied air through a demand regulator.

Augustus Denayrouze entrusted his brother Louis, a Polytechnicien (a postgraduate of France’s premier engineering university), with managing the French Society of Sponge Fishing in the Mediterranean (Société Française de Pêche des Éponges en Méditerranée), based in Smyrne, which he founded in 1865. Louis Denayrouze (1848- 1910) invented the underwater ear trumpet, the first medium of communication under the sea, and the “aerophore”, an underwater watertight gas lamp supplied by air from the diver’s air reservoir.^11,12 The Rouquayrol-Denayrouze company also produced a diving suit with an integrated, bolted-on helmet that was connected to the surface by a safety rope and rubber tubing. This equipment made extended underwater stays possible, but the hoses and ropes limited the movement of the diver.¹¹

Adventures of the “Trois Mousquemers”: the Silent World

In modern times in France and throughout the world, three Frenchmen have made an indelible mark on underwater diving: Philippe Tailliez (1905-2002), Frédéric Dumas (1913-1991), and Jacques-Yves Cousteau (1910-1997), nicknamed the “Trois Mousquemers” (the Three Musketeers of the Sea). They were undisputed pioneers in the continuous improvement of diving techniques, the development of underwater exploration, the making of documentaries, and in proclaiming the fragility of marine environments. Cousteau declared, “In our team, I was the organizer, Tailliez was the poet and visionary, and Dumas was the star.”^8,13

At this time at the end of the 1930s, divers still had rudimentary equipment. The “Rouquayrol-Denayrouze diving apparatus” had been forgotten, and divers now favored an opencircuit diving suitmade byGaston Le Prieur andMaurice Fernez (1926), which was equipped with a “manodétendeur” (flowmeter), continuous air flow, and a compressed air supply in a Michelin bottle. The diver also had a basic mask with a porthole. The drawbacks to this equipment were that a lot of air was wasted and autonomy was very limited, with only 10 minutes dive time at 12 meters.^8,13,14

It was in this environment that Philippe Tailliez—the son of a sailor, student of the Naval School of Brest, and swimming champion—moved to Toulon, where he indulged his passions for apnea diving, underwater hunting, and undersea scenery. On board the battleship Condorcet, where he was a torpedo boat officer, he met a young Lieutenant, a gunner by the name of Jacques-Yves Cousteau, whom he quickly initiated into the world of diving. In 1938, off the islands of Embiez, he met the engineer Frédéric Dumas, an adept underwater hunter and inventor, and the dynamic trio was formed. In 1942, Cousteau set about improving the currently available, but rudimentary, diving equipment. Drawing inspiration from the apparatus used by Georges Commeinhes to establish his 53-meter underwater diving record in Marseilles, he designed a new type of miniature automatic regulator made from Bakelite (although, in reality, it was still based on the Rouquayrol- Denayrouze system). This particular model of streamlined diving apparatus made by Cousteau and Emile Gagnan, a French-Canadian engineer specializing in gases, included a pressure gauge, alarm, and steel or aluminum bottles—which the inventors called an “Aqualung.” It was using this apparatus that Frédéric Dumas established a new 72-meter diving record.^8,13,15

In 1942, the first French underwater film, Par dix-huit mètres de fond (18 Meters Deep), was created by Cousteau, who filmed Dumas while diving. The film won him the Congress of Documentary Film’s first prize in 1943. The following year a second film was made, Épaves (Shipwrecks), which detailed the exploration of the boats of the French fleet that had sunk near Toulon. Cousteau, enthralled by underwater images and different perspectives, put a 35-mm camera in a watertight box, conceived by the engineer Léon Vèche (the first model wasmade in 1893 by the French biologist Louis Boutan [1859- 1934]), and the rest is history.^8,13,15

Photomontage showing the “Aqualung”, a twin-hose open-circuit scuba developed by Emile Gagnan and Jacques-Yves Cousteau in 1943.

From left to right: Jacques-Yves Cousteau in 1985, with his trademark red wool-knit cap. © AFP. Poster of Cannes Festival Golden Palm award-winning film The Silent World by Jacques-Yves Cousteau and Louis Malle (1956). © SIPA Press.

In 1945, the GRS (Groupe de Recherche Sous-Marine [Underwater Research Group]) was created under the direction of Philippe Tailliez, who had at his side both Dumas and Cousteau. On board the sloop Elie Monnier, the GRS team carried out its first extensive scientific investigations: underwater archaeology, minesweeping, exploration of the sea floor, oceanographic filming, and research with bathyscaphes (freediving, self-propelled deep-sea diving submersibles).

In 1949, Philippe Tailliez wrote the first manual on underwater diving with a diving suit. In France and throughout the world, he remains the discrete instigator of environmental awareness regarding the fragility of the marine depths: “Every man has two homelands: his own and the sea.”

Dumas continued to improve the diving equipment by inventing a safety collaret (or safety harness) in 1950, which was the first stabilizing buoyancy compensator with an air reserve separate to that of the main air supply. He also designed a groin strap, to make the carrying of air bottles easier. Dumas was also the coauthor of and the main actor in many of the films created by Cousteau on board the Calypso.^7,8,13,15,16

Jacques-Yves Cousteau: an ecological pioneer

Jacques-Yves Cousteau, the son of a lawyer, discovered the sea in the deep, rocky inlets near Marseilles where his family lived. He married Simone Melchior in 1937, and they had two children, Jean-Michel (born in 1938) and Philippe (born in 1940). Cousteau studied at the Naval School of Brest before joining the French Naval Intelligence Service. He was sent to Shanghai and Japan in 1938, to the USSR in 1939, and participated in a commando raid against the Italian intelligence services in France in 1943. In 1948, with the filmmakerMarcel Ichac (1906-1994), hemade the first underwater archaeology film, while exploring a Roman shipwreck off the coast of Mahdia (Tunisia). The film, Carnet de plongée (Diving Log), was presented at the 1951 Cannes Film Festival, where it was received with great acclaim and swept up awards.^<7,8,16

The following year, Cousteau founded the COF (Campagnes océanographiques françaises [French Oceanographic Campaigns]) and took possession of the legendary laboratory ship Calypso, which was acquired and equipped with the help of Loel Guinness (1906-1988), a descendant of Samuel Guinness, the younger brother of the Guinness brewery founder Arthur Guinness. This event marked the start of a multitude of exploratory expeditions across the oceans, seas, and rivers of the world. In the 1950s, with the help of Jean Mollard, he created the Soucoupe Plongeante SP-350, an easy-to-handle underwater “diving saucer” able to reach a depth of 350 meters. In 1956, he was awarded the Palme d’Or (Golden Palm) at the Cannes Film Festival for his film Le Monde du Silence (The Silent World), which he made with Louis Malle (1932-1995). During filming, the filmmaker suffered a barotrauma of the tympanic membrane.^7,16,17 In 1957, Cousteau was elected to the board of the Oceanographic Museum of Monaco and entered the American Academy of Sciences. His popularity continued to grow and he fought for marine ecology, organizing a press campaign in October 1960 to oppose the dumping of radioactive waste in the Mediterranean by the Commissariat à l’Énergie Atomique (French Atomic Energy Commission). During a visit to Monaco, General de Gaulle (1890-1970) asked him to be “kind” to the learned French atomic physicists. Cousteau countered: “It is up to your atomic physicists to be kind to us.”

Commander Cousteau and his crew donned red caps like those worn by the convicts from Toulon prisons forced to labor underwater, at the beginning of their underwater odyssey, which started in the early 1960s. The most media-savvy of the underwater divers, Cousteau had enormous success in the United States and, in 1977, he was awarded the United Nations Prize for the Environment. Eleven years later in 1988, he was inducted into the distinguished French body l’Académie française (French Academy).^7,16,17 In explaining his philosophy, he declared: “My goal is not to instruct; I am neither a scientist nor a teacher. I am a discoverer, and my aim is to fill people with wonder. We love what fills us with wonder, and we protect what we love.”

Cousteau created a new genre of scientific communication that mainly targeted the general public, the production of which enabled him to defend his beliefs and views on marine ecosystem conservation. His ability to amaze his audience helped introduce environmental adventure films to the genre of film documentaries. _

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